Bi-directional centrifugal pump

ABSTRACT

An impeller for a bi-directional single impeller centrifugal pump characterized by a blade configuration capable of pumping water at different capacities from a common pump cavity to either of two outlets depending upon the direction of rotation of the impeller. The capacity of the pump is generally much larger through one outlet than the other. In order to prevent unwanted discharge through the higher capacity opening when the impeller is rotating to pump through the other opening, each of the impeller blades includes a blocking segment at the discharge end of the blade which is defined by a circumferential extension of the blade having a center of curvature at essentially the axis of rotation of the impeller and extending for a distance from the blade discharge end.

United States Patent 11 1 Wassmann A-ug.7,1973

[ BI-DIRECTIONAL C ENTRIFUGAL PUMP [75] Inventor: William A. Wassmann,Mansfield,

[21] Appl. No.: 166,096

' ,4 rrorney j- H. Hen

ltaly 4l5/l52 Switzerland 416/178 Primary Examiner-Henry F. RaduazosSnTFred A, Winans e? T [57] ABSTRACT An impeller for a bi-directionalsingle impeller centrifugal pump characterized by a blade configurationcapable of pumping water at different capacities from a common pumpcavity to either of two outlets depending upon the direction of rotationof the impeller. The capacity of the pump is generally much largerthrough one outlet than the other. In order to prevent unwanteddischarge through the higher capacity opening when the impeller isrotating to pump through the other opening, each of the impeller bladesincludes a blocking segment at the discharge end of the blade which isdefined by a circumferential extension of the blade having a center ofcurvature at essentially the axis of rotation of the impeller andextending for a distance from the blade discharge end.

4, Claims, 3 Drawing Figures 1 'BI-DIRECTIONAL CENTRIFUGAL PUMPBACKGROUND OF THE INVENTION l. Field of the Invention This inventionrelates to a bi-directional centrifugal pump having a single impellerand more particularly to an improvement in an impeller for such a pump.

2. Description of the Prior Art Bi-directional single impeller pumps arewell known in the art and are advantageously employed in automaticwashing machines. In such machines, especially the type commonlydescribed as center-post agitators wherein a reversible electric motoris used which drives an agitator to provide a washing operation and, inthe reverse direction, spins the tub containing the clothes at arelatively high speed to centrifuge the water therefrom, it is desirableto be able to either pump the wash water to a drain, as during thecentrifuging operation, or pump the water through a recirculating linecontaining a lint filter, as during agitation or washing operation.

Single impeller pumps ideally lend themselves to such application asthey require only one outlet from the clothes tub into the single inletof the pump. Also, the particular discharge or outlet of the pumpdesired to be used is dependent on the mode of operation of the machinewhich in turn is directly related to the direclowing criteria: theability to pump sudsy water; efficient enough to completely pump-out thetub including any remaining foamy suds; sufficiently large capacity whenpumping to drain so that relatively little time is required to pump-out,and a much smaller capacity for pumping in the reverse direction, torecirculate the water through the filter in a manner that canaccommodate the flow.

The bi-directional single impeller pumps of the prior art generallysatisfactorily accomplished all of the above objectives, however, asboth outlets always remained open to the pumping chamber it was notuncommon that such pumps exhibited an undesirable characteristic ofpermitting atrickle of water to be pumped to the drain outlet during therecirculation mode of operation. Over the length of the wash oragitation mode, this trickle could account for a relatively large amountof water (e.g., up to 5 gallons) being lost before the wash cycle wascomplete and adversely affected the washing capability of the machine.It is acknowledged that proper valving of the drain line of the pumpcould reduce and/or eliminate such trickle but, in this highlycompetitive environment in which the pump was used, such solution wouldadd an additional prohibitive expense. The present invention obviatesthis problem with the blade configuration of the impeller.

SUMMARY OF THE INVENTION The impeller of the present invention isemployed a bi-directional centrifugal pump and generally has an arcuateblade construction with the addition of a circumferential segmentcontinuing from, and unitary with, the blade discharge end.

In the direction of rotation of the impeller to cause the pump topump-out to drain, the circumferential segment trails the discharge endof the blade and has essentially no effect on the capacity of the pump.However, in the opposite direction of rotation, i.e., to recirculate thewater, the circumferential segment leads the discharge end andeffectively eliminates the unwanted flow through the drain outlet by:reducing the efficiency of the blades in this direction; substantiallyrestricting the flow path of the water to the drain outlet; and,providing a surface moving generally in a direction opposite to thatrequired by the water if it is to flow to the drain outlet. The netresult is believed to be that the pressure developed in the pumpadjacent the drain outlet is insufficient to overcome the abovecombination to produce any water flow through the drain outlet, therebyeliminating unwanted loss of water during recirculation.

DRAWING DESCRIPTION FIG. 1 is a plan view of the impeller of the presentinvention a pump housing;

FIG. 2 is an isometric view of the impeller; and

FIG. 3 is a plan view of a blade for purposes of illustrating a vectordiagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT The impeller 10 of the presentinvention is shown in FIG. I, disposed within the lower housing member12 of a centrifugal pump ll, which is completed by a mating top housingmember 13 (only a portion of which is shown) including a central inletopening as bounded by an inlet nipple l5 to define a pump cavity orchamber 17.

The annular wall 14 of the lower housing member 12 defines two openings16 and 18, with associated outwardly projecting nipples 20 and 22integral with the housing and on which hoses (not shown) can be mountedfor directing the water-discharged from each outlet. It is noted thatopening 16 is so disposed in the housing that its outermost wall 24 issubstantially tangential to wall 14 whereas opening 18 is disposedsomewhat inboard of a tangential position. Also, opening 18 is of asmaller diameter than opening 16. These two characteristics inconjunction with the shape of the impeller blades, which will bediscussed later, and abutment members 26, 28, and 30 projecting inwardlyfrom the annular wall generally adjacent the openings, and defining whatwere previously referred to as dams, determine the discharge capacity ofthe pump for each outlet, with the capacity to pump out to drain throughopening l6'being much larger, and on the order of 20 gpm, than torecirculate through opening 18, which is on the order of 6 gpm.

The impeller 10 of the pump is characterized as a semi-enclosed impellerin that it'has a single bottom wall 34 supporting a plurality of blades36 and is open at the top adjacent the pump inlet.

Wall 34 is generally contoured so as to conform to the configuration ofthe pump cavity and to this end has an outer, generally planar, annularportion, 38 integral with a frustro-conical inner portion 40 forreceiving the bearing and sealing structure (not shown) between the pumphousing and the drive shaft (also not shown) of the drive motor of thewashing machine. A central hub portion42 of the impeller comprises asleeve-like member for receiving the drive shaft and is keyed for adirect drive connection between the impeller and the motor.

The blade configuration is clearly shown in FlG. 1. Referring thereto,each blade 36 is seen to have an arcuate profile, i.e., the blade shapeas viewed in a plane perpendicular to the axis of rotation, which can bedivided into at least two distinguishable arcuate portions referred tohereinafter as the pumping segment 44 and the blocking segment 46.

The pumping segment 44 is similar in profile to known curved centrifugalimpeller blades. The blocking segment 46, however, as distinguished fromthe generally outwardly radiating pumping portion, has no radialcomponent in the are it defines and extends only circumferentially alongthe outer periphery of the impeller bottom wall 34. These two separatearcuate segments are preferably integrally molded and blend together tomaintain a generally smooth face 48, but with a definite knee 50 formedat their juncture.

THEORY OF OPERATION As is well known in centrifugal pump theory, thefunction of the impeller is to impart velocity to the water or fluidtherein and the function of the housing or pump cavity is to transformthis velocity into a pressure. The theoretical absolute velocity, bothdirection and value, transmitted to the fluid can be determined from arepresentative vector diagram of the separate component velocities. Sucha diagram is shown in FIG. 3, and in the ensuing discussion of theory asto why it is believed that the impeller blades function to give theimproved results observed is used to illustrate these velocitycomponents and their relationship to the shape of the blade. However, inthis diagram the disclosed vectors are not to be considered asillustrating the actual value of the velocities developed by the pump.

Thus referring to the vector diagram of FIG. 3, and more specificallythe diagram having symbols with a subscript 1, which designates thevectors for counterclockwise rotation of the impeller, u represents thetangential speed of the exit point of the blade in a directionperpendicular to the radial line to this point dependent upon the rpm ofthe impeller in this direction, whereas w represents the relativevelocity of the water with respect to the blade in a directiontangential to the curvature of the blade at its exit. The theoreticalvelocity is a combination of the above relative velocities and isrepresented in direction and amount by 0,. The above analysis is takenat the knee 50 as this is the radially outermost point of the pushingsegment 44. lt is seen that the blocking segment 46 is ineffective forpumping in that the tangential speed and the relative velocity of thewater would be represented by equal and directly opposite vectorsthereby cancelling each other so that this segment produces no velocityin the water.

Therefore, analysis of the above vector diagram shows that thetheoretical outward velocity 0, is the same velocity that would be shownin a similar vector analysis of the previous blade, and that duringpumpout, the blocking segment 46 does not theoretically affect theability of the impeller to pump.

Still referring to FIG. 3 but more specifically to the vector diagramwith subscripts 2 which again represents velocity components, but inthis instance in the clockwise direction of rotation of the impellerwhich is the direction it rotates for recirculation, u, again representsthe tangential speed of the outermost point of the pumping segment ofthe blade and w, the relative velocity of the water with respect to theblade. From these two components the theoretical velocity is shown as 0However, it is seen that, in this instance, the direction of c, is intothe blocking segment 46 of the blade. Thus, in order to change thedirection of the water to flow around the blocking segment, 0 must beseparated into a component c tangential to the blocking segment and acomponent c radial to the blocking segment. Thus, a represents theavailable theoretical velocity to be changed to pressure with thedifference between 0, and c representing the loss in velocity caused bythe blocking segment. Therefore, in the clockwise direction, theblocking segment in fact lessens the efficiency of the pumping blade bya definite amount. (For a more detailed review of the theory of acentrifugal pump see Pump Handbook, Volney C. Finch, i948, pps. 37-41.)

It is also noted (see FIG. 1) that whereas the blocking segment 46trails the pumping segment 44 when the impeller is rotatedcounterclockwise, i.e., for pump-out, and does not interfere with thepumped fluids access to discharge opening 16, the blocking segment 46leads the pumping segment when the impeller is rotated clockwise forrecirculation. As it leads the pumping segment it has the effect, incooperation with dam 26, of blocking flow around the blade 36 once theblocking segment 46 becomes adjacent to the dam 26, until the pumpingsegment 44 becomes adjacent the dam. Also the blocking segment 44 hasthe effect of progressively narrowing the available passageway (from anopening having a width -ato an opening of width -b-) for the pumpedfluid to be accessible to the opening 16, as the blocking segment movesby the opening 16. And, the later point in time when the blockingsegment has completely moved by the darn 26 for the opening 16 to begenerally accessible, the direction that the pumping segment of theblade is directing the water is generally opposite to that required forany flow into opening 16.

Thus it is seen that whereas the blocking segment had no theoreticaleffect on the capability of the pump to pump to the discharge opening 16in counterclockwise direction, it has great effect in reducing theability of the pump to discharge water through this opening 16 whenrotating clockwise. This is the desirable feature of the blockingsegment 46 in that it eliminates loss of water during recirculation.

WORKING EMBODIMENT The impeller of the preferred embodiment shows sixblades equally placed on the generally annular planar portion 38 of theimpeller bottom wall having an inner diameter of approximately one andone-half inches and an outer diameter of about 3.8 inches. The bladesare generally of constant height of 0.73 inches above the bottom wall.The arcuate blade is preferably formed as a combination of threeseparate arcs with the inlet of the blade defined by an are having a0.625 inch radius blending into an are having a 1 inch radius to formthe pumping segment 44 of the blade.

The blocking segment 46 is formed by a radius equal to and on the samecenter as the outer radius of the impeller'bottom and continuing fromthe termination of the pumping segment (knee 50) for at least one-halfinch. It is felt that it is important that the blocking segment 46 ofthe blade has a center of curvature at essentially the center ofrotation of the impeller, as this configuration, as previously stated inreference to the vec-,

tor diagrams, develops no pumping pressure and therefore is singularlyapplicable as a blocking member to eliminate unwanted discharge throughthe relatively large pump-out opening 16 when the pump is pumping torecirculation.

It has been found that the abovedescribed impeller, when used in thedescribed housing and operating under substantially the same conditionsas the previously utilized pumps, has a greater ability to pump-out thefoamy suds (i.e., removes it from the tube in less time) than theseprevious pumps, and thus offers an added inherent advantage.

I claim:

1. In a bi-directional centrifugal pump having a housing defining asingle inlet and a plurality of outlets, a single impeller rotatablymounted within said housing for selectively pumping the water throughsaid outlets depending upon the forward or reverse direction of rotationof said impeller said housing further having restrictions generallyadjacent said outlets on the downstream side thereof to assist indetermining the flow rate and forcing the flow through said outlets saidimpeller being of the reversible type having blades thereon, each ofsaid blades having as viewed in a plane perpendicular to its axis ofrotation, an arcuate profile continuous through its width defined by atleast two distinct arcuate segments, with one of said arcuate segmentsdescribing an are having a component extending radially with respect tosaid impeller and at least another of said arcuate segments describingan are having a center of curvature at the axis of rotation of saidimpeller, said at least another arcuate segment of said blade therebyproviding only a circumferentially extending component with respect tosaid impeller for effectively performing a blocking function withrespect to at least one of said outlets during rotation of said impellerin one direction.

2. Structure according to claim 1 wherein said at least another of saidarcuate segments comprising a circumferentially extending componentforms the radially outermost extremity of said blade.

3. Structure according to claim 1 wherein said pump housing furtherdefines a generally annular pump cavity having a circular outer wall andwherein at least one of said plurality of outlets comprises a relativelylarge opening through said outer wall, said large opening boundedexternally of said housing by an integral conduit the outermost wall ofwhich is substantially tangential to said circular outer wall, and atleast another of said outlets comprises a relatively smaller openingthrough said outer wall bounded exteriorly of said housing by anintegral conduit extending in substantially the same direction andgenerally parallel to said first named conduit and radially inboard fromsaid circular outer wall, the smaller opening further bounded inwardlyof said housing by said restrictions including opposed facingprojections, and another of said restrictions projecting inwardlyadjacent said larger opening and generally in opposed facing relation tosaid tangential outermost wall of said conduit bounding said largeropening said projections cooperating with said blades to determine therelative flow out said outlets.

4. Structure according to claim 3 wherein said another of saidrestrictions extend internally to a position substantially adjacent thenormal path of said circumferential segment of said impeller blade.

' s s a s a j

1. In a bi-directional centrifugal pump having a housing defining asingle inlet and a plurality of outlets, a single impeller rotatablymounted within said housing for selectively pumping the water throughsaid outlets depending upon the forward or reverse direction of rotAtionof said impeller said housing further having restrictions generallyadjacent said outlets on the downstream side thereof to assist indetermining the flow rate and forcing the flow through said outlets saidimpeller being of the reversible type having blades thereon, each ofsaid blades having as viewed in a plane perpendicular to its axis ofrotation, an arcuate profile continuous through its width defined by atleast two distinct arcuate segments, with one of said arcuate segmentsdescribing an arc having a component extending radially with respect tosaid impeller and at least another of said arcuate segments describingan arc having a center of curvature at the axis of rotation of saidimpeller, said at least another arcuate segment of said blade therebyproviding only a circumferentially extending component with respect tosaid impeller for effectively performing a blocking function withrespect to at least one of said outlets during rotation of said impellerin one direction.
 2. Structure according to claim 1 wherein said atleast another of said arcuate segments comprising a circumferentiallyextending component forms the radially outermost extremity of saidblade.
 3. Structure according to claim 1 wherein said pump housingfurther defines a generally annular pump cavity having a circular outerwall and wherein at least one of said plurality of outlets comprises arelatively large opening through said outer wall, said large openingbounded externally of said housing by an integral conduit the outermostwall of which is substantially tangential to said circular outer wall,and at least another of said outlets comprises a relatively smalleropening through said outer wall bounded exteriorly of said housing by anintegral conduit extending in substantially the same direction andgenerally parallel to said first named conduit and radially inboard fromsaid circular outer wall, the smaller opening further bounded inwardlyof said housing by said restrictions including opposed facingprojections, and another of said restrictions projecting inwardlyadjacent said larger opening and generally in opposed facing relation tosaid tangential outermost wall of said conduit bounding said largeropening said projections cooperating with said blades to determine therelative flow out said outlets.
 4. Structure according to claim 3wherein said another of said restrictions extend internally to aposition substantially adjacent the normal path of said circumferentialsegment of said impeller blade.